This case-control study will evaluate a broad range of potential risk factors that may be involved in ovarian cancer etiology: reproductive, hormonal, nutritional, genetic, occupational, etc. Attempt will be made to assess the differential interaction of these factors in various disease subentities manifested by histologic, hormonal and other tumor characteristics. It will include about 400 incident cases of ovarian cancer occurring in Israel during two and half years, and 800 controls matched by age and ethnicity (400 surgical and 400 neighborhood). Emphasis will be made on the role of risk factors in high and low risk populations i.e. the two main ethnic groups of the Israeli Jews which differ in their life styles and relevant exposures. This gradient in incidence is similar to the one between white/black populations in the U.S. Thus, the results will be applicable to the U.S. community.